Your model Holmes HAP-291 uses the APF-5 Holmes Foam Air Cleaner Prefilter 2 pack APF-5 The Holmes APF-5 fits the following model of air purifier:
Holmes HAP-291
The Holmes Foam Air Cleaner Prefilter 2pk APF-5 will remove large particulates from your indoor air. This air purifier replacement filter will extend the life of HEPA an